questions about building a cedar wood framed greenhouse with a foundation

Would twenty by twenty be too large? too square?

I have a wonderful spot for one....and a son with a sawmill and a background in construction, a collection of windows and most of all (it hardly ever happens) some cash to do an appropriate foundation/drainage system and pay for the construction.

I'm not wanting to grow 'tropical' stuff...mainly start plants and winter over a few things and grow greens for us and local markets.  And I want to put our glider and some chairs out there for winter afternoons so I suppose it could be called a solarium as well?

There is always the option of a small woodstove (maybe an rmh) for extra heat in the future.

The plan is still flexible......just working with graph paper and pencil now with measurements from the site.

thanks for any thoughts.....

I can't think of any reason it wouldn't work well for what you want Judith.
Green houses can be any dimensions a person wants, it is pretty silly that most of them are rectangular in shape these days but I think it is more convention than design.
In the 1800's there were lots of conservatories built that were square in foot print and a conservatory is just a green house with an extra tall roof.
Many of those even had furniture inside for people to sit at and have tea or other refreshments.

Redhawk

Maximizing winter sun exposure is the only reason I can think of to not build in a square.
Will it be attached to your home?

Maximizing winter sun exposure is the only reason I can think of to not build in a square.
Will it be attached to your home?

These were some of my questions.  It really depends on what you want from it.  The more rectangular it is, the more broad side is facing the south, and thus the more light that is penetrating.  

The glass of the south wall will only be able to penetrate sunlight so deep unless the south wall is really tall, or really sloped, or the roof is also glazed (be sure to use tempered glass if you are going to put glass on a slope or on the roof.  

And I want to put our glider and some chairs out there for winter afternoons so I suppose it could be called a solarium as well?

There is always the option of a small woodstove (maybe an rmh) for extra heat in the future.  

The term solarium, from my understanding is generally used to describe a south wall of glass, with solid walls and roof (often these are insulated) and this is part of a sunward portion of a home, so this doesn't really fit that description.... but...  Having a hang out space in the greenhouse is a great idea, particularly with a RMH to hang out near, so it doesn't matter if you call it a solarium or a greenhouse... it's your hang out space and growing space.  

Considering that you have access to a sawmill, you do not really need to work with specific dimensions, or I would suggest doing things in multiples of 8' or 4' since that is the standard length of lumber.    

thanks everyone....the greenhouse won't be attached to the house but connected by a short covered walkway.

yes, 'conservatory' rather than 'solarium'  

A few other things came up that have me adjusting the measurements already.......we are on a dead end street and in a very small town with no (enforced) building codes....but...it appears that no one builds as close to the street as I had wanted this, so rethinking dimensions again.

The whole town is laid out in a way that our house faces south/west so I'm looking at a South/west facing greenhouse in the space available.  It can stretch for a long ways to the north west though and now might need to be limited to a sixteen foot depth....the twenty foot square would have given it more southern exposure.

going out with a compass later for more accurate readings...there is an empty lot (we own) between us and the last house on the road and I don't want to interfere with their view.  

I knew that once I began to plan and ask questions that complications would come up...this is just the beginning I guess.....thanks!

hey judith,
just a few thoughts.

please plan for proper ventillation.

could you add a "kitchen area" for processing stuff, canning, dehydrating etc.?

you could plan a dehydator-setup above the RMH barrel

what about rain water catchment? you could store that inside the greenhouse in black barrels/tanks. this adds thermal mass

have you thought about building some thick walls as thermal mass? i think, in the north and east. maybe just half height walls. you could use cob, earthbag or rammed earth. is this calles "trombe-wall"?

have you thought about building some thick walls as thermal mass? i think, in the north and east.

 I think that North is a good choice.  Many designs, if they are to incorporate another glazed wall besides the south, they would choose East to allow the morning sun to enter to begin heating and giving light to the greenhouse as early in the morning as possible.  If I was going to insulate and build thermal mass into only one other wall besides the North, I would choose West.  The reason for this is that by the time the South wall has had it's full blast of the day's sun, usually a greenhouse is up to and maxing it's temperature and needs some ventilation, and if given extra light/heat from the West this just exacerbates this problem.  I would tend to block West light and insulate this wall from the outside while having thermal mass on the inside.

Tobias Ber wrote:hey judith,
just a few thoughts.

please plan for proper ventillation.

could you add a "kitchen area" for processing stuff, canning, dehydrating etc.?

you could plan a dehydator-setup above the RMH barrel

what about rain water catchment? you could store that inside the greenhouse in black barrels/tanks. this adds thermal mass

have you thought about building some thick walls as thermal mass? i think, in the north and east. maybe just half height walls. you could use cob, earthbag or rammed earth. is this calles "trombe-wall"?

hi Tobias and thanks for your suggestions.....we're still planning the size and shape and location but yes, ventilation is part of that, not sure exactly where and how until other considerations are settled.  Have you used any of the automatic heat sensitive vents?  I like the idea of that rather than having to keep on top of opening and closing things manually.

A kitchen area would be great...good for cooking but maybe not dry enough for dehydrating?

I have some barrels and a source for more food grade 30 gallon ones.  I've been thinking about them on the inside of the north wall....and gutters on the north side to fill them...

The north wall will be an insulated wall with earth berm on the outside and the barrels on the inside (I think at the moment).

Roberto wrote: I think that North is a good choice.  Many designs, if they are to incorporate another glazed wall besides the south, they would choose East to allow the morning sun to enter to begin heating and giving light to the greenhouse as early in the morning as possible.  If I was going to insulate and build thermal mass into only one other wall besides the North, I would choose West.  The reason for this is that by the time the South wall has had it's full blast of the day's sun, usually a greenhouse is up to and maxing it's temperature and needs some ventilation, and if given extra light/heat from the West this just exacerbates this problem.  I would tend to block West light and insulate this wall from the outside while having thermal mass on the inside.

I've just now faced the fact that it is going to need to be farther from the house to receive the best winter sunlight......facing south will put it at an angle to the rest of the buildings in the neighborhood but I think it could be done so it won't look too out of place.

I like the idea of insulating the west wall also and not the east.....especially if we can orient it to receive the earliest morning sun.  
For sure we will insulate the north wall.

thanks!

I like the idea of insulating the west wall also and not the east.....especially if we can orient it to receive the earliest morning sun.  
For sure we will insulate the north wall.

 I did not want to take away from Tobias' point to put thermal mass in these walls, which in my mind is equally important to insulating.

Roberto pokachinni wrote:

I like the idea of insulating the west wall also and not the east.....especially if we can orient it to receive the earliest morning sun.  
For sure we will insulate the north wall.

 I did not want to take away from Tobias' point to put thermal mass in these walls, which in my mind is equally important to insulating.

I might be confused... the barrels of water will be inside on the north wall...that's considered 'thermal mass'?  and the earth berm at the outside of the north wall would be also?  I'm not sure how to put thermal mass 'in' the walls?  

I might be confused... the barrels of water will be inside on the north wall...that's considered 'thermal mass'?  

Yes, you are right the barrels would definitely be considered thermal mass.  As a side note: it is best with water barrels that they be black, and be, as much as possible in direct gaze of the sun.  

and the earth berm at the outside of the north wall would be also?

The Earth Berm mass outside of your structure would not be beneficial in terms of thermal mass since you are planning at this point to have insulation in between that and your space, which stops the heat from coming to and from your mass.  What it will do, is utilize that earth berm as an addition to your insulation/isolation from heat loss due to it's thermal inertia effects, stabilizing the temperature that is adjacent to the wall.  

I'm not sure how to put thermal mass 'in' the walls?  

Imagine the walls as a double wall, insulated on the outside, but with a thermal mass wall on the inside of the structure.  Brick, stone, cob, concrete, rammed earth, Sand infill.... lots of options but can be labor, time and cost intensive.  The mass absorbs the heat, the insulation keeps the heat from escaping out the back, the mass re-radiates into the space.  Maybe not necessary, if you have water barrels, and/or a RMH.  

dehydrating... i meant like a setup where you have kinda kitchen. a place to process foods. and then use an electric dehydrator or build a setup above the barrel of the RHM. like a metal box with drawers (wire mesh bottom) for the food. painted black with good solar exposure that might work well. powered by sun at day, by RMH in the evening.
if that works out for your conditions.

i don t have experience with these ventillation thingies.

Tobias was wondering about a thermal mass storing heat in the walls of a greenhouse, asking:

is this calles "trombe-wall"?  

 A trombe wall is typically a glazed area with a narrow gap to a thermal mass.  The mass, usually a wall, usually has, but doesn't necessarily have, openings to bring the heated air from the narrow gap to a living area behind it.  Slow radiation will do this, through the wall without vents, but is less efficient.  A solarium that is attached to a house is essentially a Trombe wall space that is large enough to spend time in.  Any attached greenhouse to a house also has some qualities similar to a Trombe Wall.  If you google it, or check out wikipedia, there is quite a lot of useful written information.  

hi Tobias and thanks for your suggestions.....we're still planning the size and shape and location but yes, ventilation is part of that, not sure exactly where and how until other considerations are settled.  Have you used any of the automatic heat sensitive vents?  I like the idea of that rather than having to keep on top of opening and closing things manually.  

 Hi Judith.  I've never used these things but I am interested in them.  I usually open and close my greenhouse daily, but also always build a few small windows that stay open, so that if I forget the overheating doesn't reach the extremes that would kill the plants.

I have some barrels and a source for more food grade 30 gallon ones.  I've been thinking about them on the inside of the north wall....and gutters on the north side to fill them...

 Although it's a good idea if you are short of water to use some off the roof, once they are filled you will not have need of filling the barrels (or are you planning to irrigate in the greenhouse with your barrel water?) and so the infrastructure might be unnecessary . (?)  

Without being seen as a square 😀 Have you thought about maximising the area used for growth and minimising the amount of path . I am not sure if a square is the best fit if that is an aim.

as usual, as soon as I ask a question here things change and with all of your input I'm looking at this a bit different now.  I've given up on the idea of having it up close to the house.  Really the best location is in the lot that we have next to the house in the far opposite corner where it can face south and also get more early morning sun.

I'm looking at a size, not square anymore , of 16' by 32' and 16' tall....

Roberto, does your greenhouse have a dug foundation and some sort of drainage system?  I am going to be paying someone to do that so I guess I need to start with what will work the best and know what I'm talking about.  I want to be sure it has good drainage as we have very wet seasons usually over the winter and spring when I will be using it a lot.  I would like gravel, maybe pea gravel as the final surface for the walkways.  

thanks everyone.....